Syncthing has a mobile app and there's an app for pass called PasswordStore[0] using OpenKeychain[1] (pgp manager). I'm not a fan of putting my private key on my mobile, but if I were, this would be a nice setup.
[0]: https://github.com/zeapo/Android-Password-Store
[1]: https://github.com/open-keychain/open-keychain
Edit: yeah for ctmg support, probably have to hold out for something like PostMarketOS to save us.